In clarifier operation, solids initially found in the fluid entering the vessel settle under the influence of gravity to the vessel floor and clarified fluid flows out of the tank through ports or overflow devices. The dense solids are collected, such as, by the use of moving rakes, and removed as a sludge.
The degree of removal of solids in a basin depends on the settling velocity of the solids in a quiescent fluid, basin dimensions and the flow rate of fluid containing the settleable suspension through the clarifier. Clarifiers, however, even when equipped with inlet baffles to prevent short circuiting, provide appreciably less than ideal removal of solids from liquids and, to date, no satisfactory explanation of this phenomenon has been forthcoming nor has the solids removal been significantly improved.